The main risk of having thin bones is fragility fractures – particularly if your are old.
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Walk quickly for 10 minutes, three times a day

Weight-bearing exercise (walking, running) helps to keep bones strong. Ideally, you need a mix of “feet on the ground” activity and muscle resistance such as weights, press-ups and swimming. No one knows precisely how much exercise is needed; the NHS says adults aged 19 to 64 should do at least 150 minutes of moderate-intensity aerobic activity every week. Three 10-minute periods of fast walking every day is a good target. There is little evidence that exercise prevents fractures once you have weak bones (called osteopenia if it is mild and osteoporosis if more severe), but people who keep active into old age are less likely to fall – and if you don’t fall, you are less likely to break a bone.

Don’t smoke – especially when you are young

Smoking has an impact on bone-building cells, especially in people younger than 30, who are still accumulating bone. Smokers are at increased risk of osteoporosis and fractures and stopping smoking is likely to improve bone strength. It is a complicated association: smokers may also be thinner than the healthy weight range; if you fall but have no padding, you are more likely to fracture a bone. After the menopause, women make some oestrogen – which keeps bones strong – in their fat layer. Once your ovaries stop producing oestrogen, you can’t make much of it if you don’t have any fat.

Don’t get too thin

No one is saying that it helps to be overweight; you need to be able to keep moving, of course, and the heavier you are, the more force will land on your bones if you fall. But small-framed, low-weight people have less total bone mass. As a result, losing even small amounts of weight may result in bones that break easily.

HRT helps

Women are four times more likely than men to get osteoporosis, since their levels of oestrogen fall after the menopause. Hormone replacement therapy can help maintain strong bones and prevent fragility fractures (fractures that occur on minimal force). Once you have osteoporosis, though, it is not very effective.

You don’t need calcium supplements, but consider vitamin D

A healthy, balanced diet should provide the recommended 700 millgrams a day of calcium that you need to make new bone as old bone is replaced. There is no good evidence that calcium supplements are needed if you are at low risk of osteoporosis. There has been some concern that taking extra calcium may lead to harmful deposits around the heart, increasing the risk of heart attack. The consensus is that dietary sources are preferable to supplements, except if you can’t get enough calcium from your diet because you have a condition such as Crohn’s disease that prevents adequate absorption of dietary calcium. You need about 10 micrograms a day of vitamin D for healthy bones; 90% comes from the action of sunlight on our skin and 10% from diet (such as oily fish). People who never expose their skin to sunlight or have a restricted diet may need vitamin D supplements. The NHS recommends that breast-fed babies up to one year old and all children aged one to four should have a daily supplement, while children over five and adults should consider one in the winter months.

Don’t trip up

The main risk of having thin bones is fragility fractures. Elderly people who fall and break a hip may never regain their independence. Vertebral fractures may be silent initially, but tend to recur and can become multiple and extremely painful and disabling. One of the most useful things you can do for a frail relative or friend is check their home for potential hazards such as loose carpet. Occupational therapy assessment, to fit hand rails to steps and baths, can be accessed via local authority websites or a GP referral.

Know your risk

You are at increased risk of osteoporosis if you are elderly, female, underweight or immobile; if you have had previous fractures; and if you smoke, drink a lot of alcohol (more than 30 units a week) or take steroids for a condition such as rheumatoid arthritis. You can do your own risk assessment (there is a useful risk calculator on the University of Sheffield’s website). In some cases, a bone density scan is useful. This can be arranged by your GP, but the scan needs to be taken in context of your overall risk. If you are at high risk, you will probably be advised to have treatment to build up your bones, even if the scan is normal.